feat(server): accept Standard Schemas in inputRequired.elicit

[mattzcarey]

Fixes#662.

Summary

• allow inputRequired.elicit() to accept a Standard Schema/Zod object as requestedSchema
• convert that schema to MCP's restricted form-elicitation JSON Schema
• reuse the same schema with acceptedContent() to validate and type the response on handler re-entry
• keep deprecated Server.elicitInput() and ctx.mcpReq.elicitInput() unchanged
• reject converted validation constraints that MCP form elicitation cannot express instead of weakening them silently
• preserve the raw JSON Schema input path unchanged

The modern write-once handler works on 2026-07-28 natively and on 2025-era connections through the existing legacy input_required shim.

Release

• @modelcontextprotocol/core-internal: minor
• @modelcontextprotocol/server: minor
• no client package change

Verification

• core-internal tests: 1,327 passed
• server tests: 439 passed
• modern input_required integration coverage
• 2025 legacy-shim integration coverage
• core-internal/server typechecks
• examples typecheck
• client/server builds
• dist declaration smoke with skipLibCheck: false
• snippet sync check
• pre-push full build, typecheck, and lint

[changeset-bot]

🦋 Changeset detected

Latest commit: ea34a7d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@modelcontextprotocol/core-internal	Minor
@modelcontextprotocol/server	Minor
@modelcontextprotocol/express	Major
@modelcontextprotocol/fastify	Major
@modelcontextprotocol/hono	Major
@modelcontextprotocol/node	Major

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[pkg-pr-new]

Open in StackBlitz

@modelcontextprotocol/client

npm i https://pkg.pr.new/@modelcontextprotocol/client@2369

@modelcontextprotocol/codemod

npm i https://pkg.pr.new/@modelcontextprotocol/codemod@2369

@modelcontextprotocol/core

npm i https://pkg.pr.new/@modelcontextprotocol/core@2369

@modelcontextprotocol/server

npm i https://pkg.pr.new/@modelcontextprotocol/server@2369

@modelcontextprotocol/server-legacy

npm i https://pkg.pr.new/@modelcontextprotocol/server-legacy@2369

@modelcontextprotocol/express

npm i https://pkg.pr.new/@modelcontextprotocol/express@2369

@modelcontextprotocol/fastify

npm i https://pkg.pr.new/@modelcontextprotocol/fastify@2369

@modelcontextprotocol/hono

npm i https://pkg.pr.new/@modelcontextprotocol/hono@2369

@modelcontextprotocol/node

npm i https://pkg.pr.new/@modelcontextprotocol/node@2369

commit: ea34a7d

[felixweinberger]

SGTM

[felixweinberger]

Mostly wondering if we should be updating the elicitInput API given we want people to use inputRequired for MRTR going forward.